Yes, you can certainly register a single color (or a combination) of colors as an EU trademark, but the process is complicated. The color must have acquired distinctiveness through extensive use in commerce, meaning consumers associate that specific color with a single commercial source. For example, the Milka purple or the Louboutin red.
When claiming a color, the application must include a precise description and the relevant color code (e.g., Pantone, RAL, or RGB). A vague description such as "the color blue" is not sufficient; the specific shade must be defined precisely.
Before filing your application, please keep in mind color trademarks are most commonly granted to well-established brands that can demonstrate acquired distinctiveness through substantial evidence of use.